Optical fibers are used extensively in telecommunications systems. The light-carrying core of a typical single-mode optical fiber used in optical communications systems is exceedingly small—on the order of 8 μm in diameter. Further, typical optical fibers comprise a limited numerical aperture, which defines a limited spherical angle within which light emanating from the fiber propagates or from which light may be effectively delivered into the fiber.
Generally, optical signals delivered from optical fibers must be optically coupled to many types of optical components, such as filters, interferometers, beam splitters, etc. within optical fiber communications systems and the resulting filtered, phase modulated, split, etc. signals must be coupled back into the same or other optical fibers with a minimum of insertion loss. Such coupling requires precise (generally sub-micron) angular and positional alignment of optical fibers and other optical components during manufacture. Further, this precise alignment must be maintained, without slippage or shift, during the attachment of various optical components and housings to one another and, subsequently, during the service lifetime of the optical components or systems.
FIG. 1. shows a conventional fiber optic housing and aligning device. The prior art fiber optic housing and aligning device comprises a housing 102 containing an optical component 116 and comprising a tubular snout 104. The tubular snout 104 provides support and alignment for an optical collimator device 106 that is optically coupled to the optical component 116. The optical collimator 106 is further optically coupled to an optical fiber 108 and may either provide an optical signal 114 to the optical component 116 or receive the optical signal 114 from the optical component 116 or both.
The tubular snout 104 comprises a plurality of apertures 112 that are utilized for soldering the snout 104 to the collimator 106 after initial alignment of the collimator within the snout 104. The snout 104 may comprise one or more thinned regions 110 that are more easily deformed than the main body of the snout 104. A preliminary optical alignment of the collimator 106 with respect to the optical component 106 is performed prior to soldering or affixing with epoxy or other adhesive. The collimator 106 is then fixed in place relative to the snout 104 by applying solder, epoxy or some other adhesive to the apertures 112.
Precise optical alignment is problematical during manufacture of the conventional fiber optic housing and aligning device. Uneven heating or cooling of the tubular snout during soldering or unequal solder mass distribution amongst the apertures will generally cause some post-soldering positional shift of the collimator. This post-soldering shift will generally degrade the quality of the optical coupling between the collimator 106 and the optical component 116. This post-soldering shift must then be compensated by mechanical deformation of the snout 104. This mechanical deformation may be accomplished by bending or twisting the thinned portions 110 so as to compensate for the shift and restore optimal optical coupling between the collimator and the optical component. Alternatively, the magnitude of the post-soldering shift may be estimated beforehand and a compensating mis-alignment may be applied prior to soldering.
The post-soldering mechanical deformation required to optically align the conventional fiber optic housing and aligning device is difficult to precisely control and, thus, can lead to poor manufacturing yield. Also, the soldering of parts within the illustrated and other conventional fiber optic housing and aligning devices can lead to unequal or asymmetric solder distribution around the device. This uneven solder mass distribution can lead to uneven thermal expansion and/or contraction that during normal environmental changes during the service lifetime of the apparatus. These uneven thermal effects can lead, in turn, to gradual loss of optical alignment. There is therefore a need for an improved method and apparatus for a fiber optic housing and aligning device that does not suffer from these disadvantages.